The Effect of Systemic Angiotensin-Converting Enzyme Inhibition on Normal and Autonomous Functioning Lactotrophs

Authors: Rüştü SERTER, Necdet ÜNÜVAR, Gül GÜRSOY, Serdar GÜLER, Sani MURAT, Fahri BAYRAM, Yalçın ARAL

Abstract: There are contradictory reports about the relation between pituitary local renin-angiotensin system (RAS) and the secretory functions of lactotrophs. We evaluated the effect of the ACE inhibitor captopril on plasma prolaction, growth hormone and TSH secretion in patients with idiopathic hyperprolactinemia (n= 18) and in hypertensive patients with normal pituitaries (n=12). A slight but significant fall in plasma prolaction levels at 60 (p<0.05. p<0.01, respectively) and 120 min (p<0.05, p<0.01, respectively) after captopril administration in both of the groups was observed followed by an increase back to basal levels after two weeks. Growth hormone and TSH showed a similar course only in the hyperprolactinemic group, suggesting a relation between autonomous functioning lactotrophs and these hormones. Plasma renin activity increased permanently following ACE inhibition as expected, whilst aldosterone levels which declined following the acute inhibition, increased back to near basal levels after two weeks in both groups. The reincrease of prolactin levels at the meantime with aldosterone, which is presumably due to rise in A-ll following the decline after acute administration, strongly supports the presence of a relation between systemic RAS and pituitary prolactin secretion. Our data showed us that ACE inhibition will not affect lactotrophs permanently suggesting that A-ll antagonist agents should be tried in further in vivo studies.

Keywords: Angiotensin-converting enzyme inhibitor, Renin-angiotensin system, Lactotrophs, Pituitary, Hperprolactinemia, Captopril